In order to make a flat mop to squeeze water by itself many techniques have been developed and proposed in the past, such as China patent gazette Nos. ZL 200720192814.5, ZL 201220160635.4, ZL 201020144850.6 and ZL 201220188408.2. They all provide a self-wrung mop with a basic structure including a mop handle and a slidable wringing sleeve located thereon. The wringing sleeve is connected to a wringing head through a connection bar. The wringing head includes an opening with a wringing roller inside. A flat panel mop head can pass through the opening. Drawing the wringing sleeve upward the wringing roller can squeeze water contained in a mop cloth coupled on the flat panel mop head. The aforesaid self-wrung flat mop has a drawback: after the water is squeezed the flat mop cannot stand upright and the flat panel mop head has to leveled with the cleaning cloth laid on the floor surface. As a result, the cleaning cloth is difficult to be dried and also is prone to be dirty.